A Validated RP-HPLC Stability Method for the Estimation of Chlorthalidone and Its Process-Related Impurities in an API and Tablet Formulation

Table 8

Stability study results.

Impurities	40°C/75%RH					25°C/60%RH		Limit
	Initial	1 M	2 M	3 M	6 M	3 M	6 M
For API
Impurity B (%w/w)	ND	ND	ND	ND	ND	0.01	0.01	NMT 0.10%
Stage II (%w/w)	ND	ND	ND	0.0	0.0	ND	ND	NMT 0.15%
Stage III (%w/w)	ND	ND	0.01	0.01	0.01	ND	ND	NMT 0.15%
Single large unknown impurity (%w/w)	0.07	0.05	0.03	0.05	0.06	0.05	0.04	NMT 0.10%
Total impurities (%w/w)	0.29	0.20	0.21	0.26	0.27	0.17	0.15	NMT 0.5%
For formulation
Impurity B (%w/w)	ND	ND	ND	ND	ND	0.01	0.01	NMT 0.10%
Stage II (%w/w)	ND	ND	ND	0.0	0.0	ND	ND	NMT 0.15%
Stage III (%w/w)	0.01	0.01	0.01	0.02	0.03	ND	ND	NMT 0.15%
Single large unknown impurity (%w/w)	0.05	0.05	0.07	0.06	0.09	0.06	0.05	NMT 0.10%
Total impurities (%w/w)	0.30	0.28	0.27	0.26	0.25	0.27	0.25	NMT 0.5%

ND: not detected.